A day in the life of the rodeo cowboy. A slug of bourbon, a dance with the bull, a post-buck shuffle with a prostitute under the stands. A life of narrow parameters. Pleasure taken fast, hard and simple.

Dallas Buyers Club shows how terminal illness ripped up the routine of one such small thinker. Ron Woodroof was a homophobic hedonist who, in 1986, was given 30 days to live after being diagnosed HIV positive. His world flipped from gay-bashing in the bar with his blue collar buddies, to hours in hospital, camped next to fellow AIDs patients, most of whom were gay men dealing with a disease that had started to devastate their community.

Woodroof's response to his diagnosis was to reject his doctor's prescription, head for the Mexican black market to collect his own cocktail of alternative therapies, then set up a subscription service to shop the treatment back to the same people he claimed to hate. He was a grizzly, complex character. Dallas Buyers Club is at its best when it keeps him that way.

Matthew McConaughey lost 38 pounds to play Woodroof. He delivers a twitchy, hostile performance on par with anything he's done since he escaped the rom com cul-de-sac. He's matched by Jared Leto as Rayon, a transsexual drug addict who goes into business with Woodroof and carries the responsibility of broadening the shit-kicking cowboy's world view. Rayon paints Woodroof's motel room a garish red ("It's Cranberry Mocha!"), sticks pictures of Marc Bolan up amongst the cutouts from girlie mags. The odd couple came together because there was money to be made, but Rayon reasons it won't hurt to dripfeed Woodroof some tolerance as well. Less juicy is Jennifer Garner's role as the more sympathetic of Woodroof's doctors. "You're always in a white coat," he says. "Are you afraid of colour?". The screenplay answered in the affirmative a long time ago.

America's AIDS crisis has been under a small scale cinematic re-evaluation of late. Last year's Oscar-nominated documentary How to Survive a Plague condemned government inaction. Dallas Buyers Club takes on big pharma, waging war on the bureaucrats who were happy to charge $10,000 a year for drugs that were toxic, while the FDA stood in the way of treatments that were proven to work, but less marketable. It's in this fight that the film loses part of its thrust. The suits and their profit margins are no match for McConaughey as Woodroof. The wildcard's more fun to watch.

Dallas Buyers Club takes its own alternative route compared to the prescribed biopic conventions. There's a conversion for Woodroof, but it's not dramatic or revelatory. He didn't have enough time left to become a true reformer. He accepts and even loves Rayon, but we don't get a grand-scale happy-clappy realisation that all of us are equal. Nor should we. This is not about a community taking care of its own. This is about Ron Woodroof looking out for himself, permitting difference to that end, then growing gradually out of routine homophobia. He was a grizzled bastard who spun a profit that paved a way for change. A survivor who escaped himself through desperation and greed. Dallas Buyers Club stays true to that remarkable, redoubtable spirit.